Solar Terrestrial Activity Report

Activity chart

Last major update issued on July 21, 2013 at 03:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update July 1, 2013)] [Cycle 24 progress (last update July 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update July 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update July 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update July 1, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated June 30, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to unsettled on July 20. Solar wind speed at SOHO ranged between 376 and 573 km/s, decreasingly under the influence of a high speed stream from CH575.

Solar flux measured at 20h UTC on 2.8 GHz was 112.5 (decreasing 15.7 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5). Three hour interval K indices: 31111001 (planetary), 31222222 (Boulder).

The background x-ray flux was at the class B3 level.

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11793 [N20W03] lost some spots.There's a chance of C class flares due to polarity intermixing.
Region 11799 [S16E35] was quiet and stable.
Region 11800 [S11E38] was quiet and stable.

Spotted regions not numbered by SWPC:
S2557 [S11E55] was quiet and stable.
New region S2561 [S09E36] emerged quickly with several spots near AR 11800 and has weak polarity intermixing.
New region S2562 [S32W17] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

July 18-20: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent coronal hole (CH575) in the northern hemisphere was in an Earth facing position on July 14-19. A recurrent trans equatorial coronal hole (CH576) will likely rotate into an Earth facing position on July 22-23.

Coronal hole map

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 20-22 due to effects from CH575.

Coronal holes (1) Coronal mass ejection (2) M and X class flares (3)
     

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

(Click on image for 2K resolution) Compare to the previous day's image. 0.5k image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region Date numbered
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
11791 2013.07.10
2013.07.12
      S13W60           plage
11792 2013.07.10
2013.07.12
      N02W58        

plage

S2544 2013.07.12       N11W56           plage
11797 2013.07.13
2013.07.17
      S19W26         plage
11795 2013.07.13
2013.07.14
      S06W25         plage
11793 2013.07.13
2013.07.14
24 42 17 N21W01 0230 EAO FAI

beta-gamma

area: 0400

S2550 2013.07.15       S21W19         plage
11796 2013.07.15
2013.07.17
      S13W81         plage
S2553 2013.07.16       N13W24           plage
11798 2013.07.17
2013.07.18
1     S12E14 0010 AXX     plage
11799 2013.07.17
2013.07.18
  4   S17E34 0007   AXX  
11800 2013.07.17
2013.07.18
2 3 1 S09E37 0020 CRO HRX area: 0030

location: S11E38

S2557 2013.07.18   2   S11E55 0003   AXX  
S2559 2013.07.19       S13W10         plage
S2560 2013.07.19       N18E24         plage
S2561 2013.07.20   17 6 N09E36 0090   DRI    
S2562 2013.07.20   1   S32W17 0001   AXX    
Total spot count: 27 69 24  
Sunspot number: 57 129 54  (total spot count + 10 * number of spotted regions)
Weighted SN: 35 80 35  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 34 45 30 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2011.11 153.5 (cycle peak) 96.7 (cycle peak) 61.1 (+1.2) 5.55
2012.02 106.5 32.9 66.9 (+1.4)
possible cycle 24 max
8.81
2012.04 113.0 55.2 64.6 (-2.2) 10.10
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 58.9 (-2.8) 10.08
2012.07 133.9 66.5 57.7 (-1.2) 13.90
2012.08 115.4 63.0 58.1 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.0) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 (58.7 projected, -0.9) 4.69
2013.02 104.3 38.0 (58.3 projected, -0.4) 6.11
2013.03 111.3 57.9 (57.9 projected, -0.4) 10.56
2013.04 124.8 72.4 (57.5 projected, -0.4) 5.40
2013.05 131.4 78.7 (57.6 projected, +0.1) 9.73
2013.06 110.1 52.5 (57.9 projected, +0.3) 12.60
2013.07 119.0 (1) 60.1 (2A) / 93.2 (2B) / 58.7 (2C) (58.0 projected, +0.1) (11.12)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Boulder SN current month average to date. 2C) STAR SDO 1K Wolf number 30 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on the analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.